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RFC 791 - IP Header Option: Security

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### RFC 791 - IP Header Option: Security

This option provides a way for hosts to send security, compartmentation, handling restrictions, and TCC (closed user group) parameters. The format for this option is as follows:

    +--------+--------+---//---+---//---+---//---+---//---+
    |10000010|00001011|SSS  SSS|CCC  CCC|HHH  HHH|  TCC   |
    +--------+--------+---//---+---//---+---//---+---//---+
     Type=130 Length=11

Security (S field): 16 bits

  Specifies one of 16 levels of security (eight of which are reserved for future use).

      00000000 00000000 - Unclassified
      11110001 00110101 - Confidential
      01111000 10011010 - EFTO
      10111100 01001101 - MMMM
      01011110 00100110 - PROG
      10101111 00010011 - Restricted
      11010111 10001000 - Secret
      01101011 11000101 - Top Secret
      00110101 11100010 - (Reserved for future use)
      10011010 11110001 - (Reserved for future use)
      01001101 01111000 - (Reserved for future use)
      00100100 10111101 - (Reserved for future use)
      00010011 01011110 - (Reserved for future use)
      10001001 10101111 - (Reserved for future use)
      11000100 11010110 - (Reserved for future use)
      11100010 01101011 - (Reserved for future use)

Compartments (C field): 16 bits

  An all zero value is used when the information transmitted is not compartmented. Other values for the compartments field may be obtained from the Defense Intelligence Agency.

Handling Restrictions (H field): 16 bits

  The values for the control and release markings are alphanumeric digraphs and are defined in the Defense Intelligence Agency Manual DIAM 65-19, "Standard Security Markings".

Transmission Control Code (TCC field): 24 bits

  Provides a means to segregate traffic and define controlled communities of interest among subscribers. The TCC values are trigraphs, and are available from HQ DCA Code 530.

Must be copied on fragmentation. This option appears at most once in a datagram.

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RFC 791 - IP Header Option: Security